1. Field of the Invention
The present invention relates to a linear compressor, and more particularly, to a driving controlling apparatus for a linear compressor capable of reducing a stroke by increasing a current applied to a linear motor when the stroke is more than a top dead center (TDC), and a method thereof.
2. Description of the Background Art
Generally, a linear compressor reciprocates a piston with using a linear motion of a motor by directly connecting the piston to a mover of a linear motor.
When the linear compressor is applied to a compressor or a refrigerator, a compression ratio of the linear compressor is varied by varying a voltage inputted to the linear compressor thus to control a cooling capacity.
FIG. 1 is a block diagram showing a driving controlling apparatus for a linear compressor in accordance with the related art.
As shown, the driving controlling apparatus for a linear compressor comprises a current detecting unit for detecting a current applied to a motor; a voltage detecting unit 3 for detecting a voltage applied to the motor; a stroke estimating unit 5 for estimating a stroke by the detected current, the detected voltage, and a motor parameter; a comparing unit 1 for comparing the stroke estimation value with a stroke command value thereby outputting a difference value therebetween; and a controlling unit 2 for controlling a stroke by varying a voltage applied to the motor according to the difference value.
An operation of the related art driving controlling apparatus for a linear compressor will be explained.
The current detecting unit 4 detects a current applied to a motor, and a voltage detecting unit 3 detects a voltage applied to the motor.
The stroke estimating unit 5 calculates a stroke estimation value by using the detected current, the detected voltage, and a motor parameter. Then, the stroke estimating unit 5 applies the stroke estimation value to the comparing unit 1.
Then, the comparing unit 1 compares the stroke estimation value with the stroke command value, and applies a difference value therebetween to the controlling unit 2. Then, the controlling unit 2 varies a voltage applied to the motor thus to control a stroke.
As shown in FIG. 2, when the stroke estimation value is greater than the stroke command value, the controlling unit 2 decreases a voltage applied to the motor. On the contrary, when the stroke estimation value is less than the stroke command value, the controlling unit 2 increases a voltage applied to the motor.
The linear compressor obtains a stroke estimation value by using a motor parameter (a), a resistance (R), and a reactance (L), and controls a stroke by using the stroke estimation value.
The related art linear compressor using a stroke voltage controls a voltage by controlling an LC resonance with using a capacitor.
FIG. 3 is a flowchart showing a method for controlling a top dead center (TDC) of the linear compressor in accordance with the related art.
The controlling unit 2 judges whether or not a stroke is a TDC with increasing an input current. When the stroke is the TDC as a result of the judgement, the current applied to the linear motor is maintained.
When the stroke is not the TDC as a result of the judgement, the controlling unit 2 judges whether or not the stroke is less than the TDC. If the stroke is less than the TDC, an input current applied to the linear compressor is increased. On the contrary, if the stroke is more than the TDC, the input current is decreased.
The TDC control is performed by controlling the input current applied to the linear compressor.
However, the related art driving controlling method has the following problems.
First, when the stroke is more than the TDC, a stroke trembling phenomenon occurs even if the input current is decreased or maintained.
Second, when the input current to the linear compressor is decreased, power applied to the linear compressor is greatly increased or decreased thus to vary a cooling capacity. Accordingly, a reliability of the linear compressor is lowered.